Image forming apparatus and image forming system with correction mechanism

Abstract

An image forming apparatus and an image forming system, the image forming apparatus including a memory to store first side position and second side position detected by a side end detector, a correction mechanism to movably support at least a registration roller of a first sheet conveyor and a second sheet conveyor in a direction perpendicular to a sheet conveying direction, and a controller to calculate a deviation between the first side position and the second side position, and to set the deviation as a correction amount of the correction mechanism.

What is claimed is: 
     
       1. An image forming apparatus comprising:
 a sheet feeder, including a roller, to feed a sheet to a sheet conveyance passage; 
 an image former, including a transfer belt, to form an image on the sheet; 
 a first sheet conveyor, including a registration roller, at an upstream side of an image forming position in which the image former forms the image on the sheet, to convey the sheet along a sheet conveying direction; 
 a sheet reverser, including a guiding roller, to reverse the sheet on which the image is formed on a first face; 
 a second sheet conveyor, including a conveying roller, to convey the sheet, which is reversed by the sheet reverser, to the first sheet conveyor for the image former to form the image on a second face; 
 a first sensor to detect a rear end of the sheet in the sheet conveying direction; 
 a second sensor to detect a front end of the sheet in the sheet conveying direction; 
 a side end detector disposed near the first sheet conveyor to detect a first rear end side position of the first face when the first sensor detects the rear end of the sheet and to detect a second front end side position of the second face when the second sensor detects the front end of the sheet; 
 a memory to store the first rear end side position and the second front end side position detected by the side end detector; 
 a correction mechanism, including a movable plate, to movably support at least the registration roller of the first sheet conveyor and the second sheet conveyor in a direction perpendicular to the sheet conveying direction; and 
 a controller to calculate a deviation between the first read end side position and the second front end side position, and to set the deviation as a correction amount of the correction mechanism, 
 wherein, in a side registration correcting operation, the controller controls movement of the correction mechanism by the correction amount. 
 
     
     
       2. The image forming apparatus according  claim 1 , wherein the correction mechanism includes
 the movable plate, which rotatably supports the registration roller, 
 a cam to move the movable plate in the direction perpendicular to the sheet conveying direction, and 
 an actuator to drive the cam, 
 wherein the actuator is controlled by the controller. 
 
     
     
       3. The image forming apparatus according  claim 2 , wherein the cam is an eccentric cam. 
     
     
       4. The image forming apparatus according  claim 3 , wherein
 the actuator is a rotary actuator, 
 the memory stores a data table that includes a correspondence between a rotation angle of the rotary actuator and the deviation of the sheet, and 
 in the side registration correcting operation, the controller controls the rotary actuator to rotate by the rotation angle. 
 
     
     
       5. The image forming apparatus according  claim 2 , wherein the correction mechanism includes a spring attached to the movable plate at one end thereof. 
     
     
       6. The image forming apparatus according  claim 2 , wherein the movable plate includes a single plate that rotatably supports the first sheet conveyor and the second sheet conveyor. 
     
     
       7. The image forming apparatus according  claim 2 , wherein the movable plate includes a first movable plate and a second movable plate, the first movable plate rotatably supports the first sheet conveyor, and the second movable plate rotatably supports the second sheet conveyor. 
     
     
       8. The image forming apparatus according  claim 7 , wherein each of the first movable plate and the second movable plate is associated with a cam and an actuator. 
     
     
       9. The image forming apparatus according  claim 8 , wherein when a length of the sheet, in the sheet conveying direction, is shorter than a length of the sheet conveyance passage between the image forming position and a roller that is a most downstream roller of the second sheet conveyor, the controller controls the actuator associated with the first movable plate in the side registration correcting operation. 
     
     
       10. The image forming apparatus according  claim 8 , wherein when a length of the sheet, in the sheet conveying direction, is longer than a length of the sheet conveyance passage between the image forming position and a roller that is a most downstream roller of the second sheet conveyor, the controller controls the actuators associated with the first movable plate and the second movable plate in the side registration correcting operation. 
     
     
       11. The image forming apparatus according  claim 2 , wherein the side end detector is disposed on a side opposite the movable plate across the sheet conveyance passage in the direction perpendicular to the sheet conveying direction. 
     
     
       12. The image forming apparatus according  claim 1 , wherein the side end detector includes a contact image sensor. 
     
     
       13. The image forming apparatus according  claim 1 , wherein the controller performs the side registration correcting operation when the registration roller is conveying the reversed sheet. 
     
     
       14. An image forming system comprising:
 an image forming apparatus to form an image on a sheet; and 
 a sheet bank to store a plurality of sheets, and to feed the plurality of sheets to the image forming apparatus, wherein the image forming apparatus includes 
 a sheet feeder, including a roller, to feed the sheet to a sheet conveyance passage, 
 an image former, including a transfer belt, to form an image on the sheet, 
 a first sheet conveyor, including a registration roller, at an upstream side of an image forming position in which the image former forms the image on the sheet, to convey the sheet along a sheet conveying direction, 
 a sheet reverser, including a guiding roller, to reverse the sheet on which the image is formed on a first face, 
 a second sheet conveyor, including a conveying roller, to convey the sheet, which is reversed by the sheet reverser, to the first sheet conveyor for the image former to form the image on a second face; 
 a first sensor to detect a rear end of the sheet in the sheet conveying direction; 
 a second sensor to detect a front end of the sheet in the sheet conveying direction; 
 a side end detector disposed near the first sheet conveyor to detect a first rear end side position of the first face when the first sensor detects the rear end of the sheet and to detect a second front end side position of the second face when the second sensor detects the front end of the sheet; 
 a memory to store the first rear end side position and the second front end side position detected by the side end detector; 
 a correction mechanism, including a movable plate, to movably support at least the registration roller of the first sheet conveyor and the second sheet conveyor in a direction perpendicular to the sheet conveying direction; and 
 a controller to calculate a deviation between the first read end side position and the second front end side position, and to set the deviation as a correction amount of the correction mechanism, 
 wherein, in a side registration correcting operation, the controller controls movement of the correction mechanism by the correction amount. 
 
     
     
       15. An image forming system comprising:
 an image forming apparatus to form an image on a sheet; and 
 a finisher device to bind the sheet, which is conveyed from the image forming apparatus, with staple and fold, 
 wherein the image forming apparatus includes 
 a sheet feeder, including a roller, to feed the sheet to a sheet conveyance passage, 
 an image former, including a transfer belt, to form an image on the sheet, 
 a first sheet conveyor, including a registration roller, at an upstream side of an image forming position in which the image former forms the image on the sheet, to convey the sheet along a sheet conveying direction, 
 a sheet reverser, including a guiding roller, to reverse the sheet on which the image is formed on a first face, a second sheet conveyor, including a conveying 
 roller, to convey the sheet, which is reversed by the sheet reverser, to the first sheet conveyor, 
 a second sheet conveyor, including a conveying roller, to convey the sheet, which is reversed by the sheet reverser, to the first sheet conveyor for the image former to form the image on a second face; 
 a first sensor to detect a rear end of the sheet in the sheet conveying direction; 
 a second sensor to detect a front end of the sheet in the sheet conveying direction; 
 a side end detector disposed near the first sheet conveyor to detect a first rear end side position of the first face when the first sensor detects the rear end of the sheet and to detect a second front end side position of the second face when the second sensor detects the front end of the sheet; 
 a memory to store the first rear end side position and the second front end side position detected by the side end detector; 
 a correction mechanism, including a movable plate, to movably support at least the registration roller of the first sheet conveyor and the second sheet conveyor in a direction perpendicular to the sheet conveying direction; and 
 a controller to calculate a deviation between the first read end side position and the second front end side position, and to set the deviation as a correction amount of the correction mechanism, 
 wherein, in a side registration correcting operation, the controller controls movement of the correction mechanism by the correction amount.